Acoustical device



Dec. 21, 1937. H F, OLSON 2,102,736

ACOUSTICAL DEVICE Filed Nov. 21, 1933 I INVENTOR HARRY F. OLSON v VKKMATTORNEY granted on an application of Julius Weinberger-v tween the endpieces l5 which cover the upper to apart of the ribbon diaphragm. Thestructo' the rear of the device. This structure, howgo In accordancewith the present invention,- the 1, The b t on of magnetic fieldproducing v ph'ragm, is filled with tufts of felt or the like and theconductor and arranged t form a passage- 25 response to sound wavepressure and is of rela- The combination of magnetic flem'producmg. 30

f ther objectis toprovide a ribbon microphone 4o scope will be pointedout in the appended claims.

Patent ed Dec. 193? I v v I I UNITED STATES PATENT oFFicE arry F. Olson,Collingswood, N. J., assignor to Radiov Corporation of America, acorporation ot Delaware v Application November 21, 1933, Serial No.(99,090

6 Claims. (01. nag-13s) This invention relates generally to devices forI and pole pieces l2. To the rear of the diaphragm producing electricalcurrents which are depend- J0. and within the chamber formed by themagent on and vary as the waves of sound and, more netic structure islocated a member I3 arranged particularly, to readily portablemicrophones or to form awinding passageway or labyrinth. This 5 soundpick-up devices which are responsiveto the passageway-opens at the rearof the diaphragm pressure of a sound wave. r and may be loaded with feltfilling ll or tu'fts of A microphone responsive to both the velocityfelt for rendering theimpedancepresented to the component and thepressure-of a. sound wavevis diaphragm independent offfrequency. It willbe disclosed in United States-Patent No.- 1,892,645 noted that thediaphragm I0 is suspended beand-myself. In accordance with this patent,the and lower ends of the passageway.

diaphragm of a ribbon microphone is rendered As indicated by Fig. 4, theimpedance chamber sensitive to sound wave pressure by placing may beinthe form of a pipe"; flared at the end the opening of a pipe or conduitin juxtaposition adjacent the diaphragm and extending linearly .turedisclos y h P however is not ever, .lacks compactness and possessesother se- Suitab e o microphones h h ust be readily rious disadvantageswhere portability is an' im' portable such as thosesuspended from thecoat portant c n5ideration lapel of a speaker. Having thus described myinvention, I claim:

structure is simpl fied. the impedance presented means arranged to forma single chamber, an tothe ribbon di ph g being renderedindependelectrical conductor forming a diaphragm and ent o q e y b m aWinding P mounted in said field to form a section in the y which 18formed a the back wall of said chamber, means covering the rear of isenclosed within the magnetic structure 9 the way leading from saidconductor and within said device' i chamber, and means located withinsaidpassage- The Principal b of-the invention is to way forrenderingsaid conductor'responsive to the vide an improved microphonewhich operates in pressure of a sound tively light weight thuspermitting-it to'be sus-..- means arran 7 ged to form a chamber, anelectrifi ig gi i g g h user if desired" cally conducting diaphragmmounted in said field er Jec 0 e a r 1bbn micmphone to form a section ina wall of said chamber, means which is of relativelylight-construction.A furarranged within said chamber to form a winding v a l passagewaywith one of its openings covering the 35 whlch responds to sound wavepressure rear of said diaphragm, means within said .pas-

The invention will-be better understood from dag ent d the followingdescription when considered in con- .ig fizg ggfi g giggggg fiii 23 53?6 nection with the accompanying drawing and its 3. The combination ofmagnetic field producing means arranged to forms, chamber, an elec- 40trically conducting diaphragm mounted in said field to formla section ina'wall of said cham-l Referring to the drawing: v,

. Fig. 1 is a partly exploded view of a microphone 'tit?223%itiiiiiiiril 'iiiih...g he means. of mien-a1 a winding passageway or labyrinthinside the Filled passageway with one lts Open- 45 magnetic structure ofthedevice, n gs at the rear of said diaphragm, means with- Fig. 3 is aplan view of the front of the device L passageway for rendefmgtheimpedance I presented to the diaphragm independent of ire- Fig. 4illustrates a modified'form of the invenquencyv tion which issatisfactory from the viewpoint of t 9i magnet: fi Pmdlmmg 5o 1 'fb buts less'satisfactoryl fro t means arranged to form a chamber, anelectriviewpoint of compactness and portability. cally conductingdiaphragm mounted i i field The device of Figs. 1 to 3 includes acorrugatedto form a section in a wall of said chamber, ribbon diaphragml0 which is mounted in the means including a sheet of material looselyrolled field of a magnetic structure including a yoke H Y to form apassageway with one of its openings at 55 V 6. The combination ofmagnetic field producing means arranged to form a single chamber, an

electrical conductorforming a diaphragm mounted in said field, meansarranged to form a labyrinthian passageway having its mouth adja- 5 centsaid conductor and ieading into said chamher; and damping means locatedwithin said passageway.

V HARRY F. OLSON.

